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A171260 Numbers n such that sigma(n) = 15*phi(n) (where sigma=A000203, phi=A000010). 5
840, 11880, 12180, 25080, 32130, 67830, 79170, 172260, 282744, 312840, 363660, 569160, 596904, 634410, 696696, 843780, 846090, 959310, 996840, 1119690, 1201560, 1402440, 1542840, 1607340, 1929312, 2104440, 2247210, 2363790, 3309240, 3368040, 3883680 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..1000

Kevin A. Broughan and Daniel Delbourgo, On the Ratio of the Sum of Divisors and Euler’s Totient Function I, Journal of Integer Sequences, Vol. 16 (2013), Article 13.8.8.

Kevin A. Broughan and Qizhi Zhou, On the Ratio of the Sum of Divisors and Euler's Totient Function II, Journal of Integer Sequences, Vol. 17 (2014), Article 14.9.2.

PROG

(PARI) for(k=1, 3e6, sigma(k) - 15*eulerphi(k) | print1(k", "));

CROSSREFS

Cf. A062699, A068391, A068390, A136547, A104900, A136540, A104901, A163667, A171256, A171257, A104902, A171258, A171259, A104903.

Sequence in context: A276161 A135038 A215230 * A166758 A188781 A166764

Adjacent sequences:  A171257 A171258 A171259 * A171261 A171262 A171263

KEYWORD

nonn

AUTHOR

Farideh Firoozbakht and M. F. Hasler, Mar 19 2010

STATUS

approved

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Last modified February 22 19:59 EST 2019. Contains 320403 sequences. (Running on oeis4.)